1. Field of the Invention
This invention relates to a dosing system, especially for filling containers with a particulate/liquid mixture.
2. Description of the Prior Art
GB 2089440 A discloses a pump for metering two fluids, particularly a relatively thick fluid, such as a suspension of solid particles in a liquid, with an homogeneous liquid. The pump comprises a first cylinder containing a floating, solid, first piston and having an inlet conduit and an outlet conduit, a second piston in a second cylinder and for closing the communication between the first cylinder and its inlet conduit and between the first cylinder and its outlet conduit, alternately, the first piston drawing in the thick fluid from the inlet conduit and discharging it into the outlet conduit, and a third cylinder having a piston for drawing in the thin fluid from a second inlet conduit which piston has at least one port provided with one or more valves through which the thin fluid can flow to occupy the space between the first and third pistons where it can transmit the motion of the third piston to the first piston, and a by-pass for conveying thin fluid from the space between the pistons to the outlet conduit.
The bypass serves to feed thin fluid to inwardly directed nozzles in the lower end of the outlet conduit to inject thin fluid into the discharge section to wash away traces of the thick fluid from the lower end of the second piston and from the internal surface of the discharge section, which converges downwardly from just above the level of the nozzles. This arrangement has a number of disadvantages. Firstly, the provision of internal surface portions below the level of the lower end of the stroke of the second piston encourages dripping from the outflow mouth of the outlet conduit. Secondly, the liquid jets may be unsuccessful in preventing an accumulation of sticky substances upon the piston end surface and those internal surface portions. Thirdly, the nozzles may become clogged with particulates and are then awkward to clean.